Apparatus for controlling depth of a water-towed cable

ABSTRACT

Apparatus for controlling the depth of water-towed cables such as marine seismic cables, such apparatus being remotely controllable to run at a predetermined depth under regulation of hydrostatic pressure responsive mechanism. The apparatus consists of electrical transmission and reception circuitry operating in conjunction with the seismic cable, and being capable of controlling depth regulating mechanism to operate at one of a plurality of selected depths. The depth regulating mechanism includes first and second coacting pressure regulator devices, the first regulator device being a regulatory mechanism for varying the diving planes in accordance with the differential between the ambient hydrostatic pressure and a pre-set volume of gas under selected pressure, the second device functioning as a servo-follower mechanism to select and control the amount of gas pressure within said pre-set volume at the specified depth.

[451 Aug. 1, 1972 [54] APPARATUS FOR CONTROLLING DEPTH OF A WATER-TOWEDCABLE Bill Smith, Ponca City, Okla.

Continental Oil Company, Ponca City, Okla.

Filed: Sept. 25, 1970 Appl. No.1 75,387

U.S. Cl. ..l14/235 B, 340/7 PC Int. Cl. ..B63b 21/00 Field of Search ..114/235 B; 340/7 PC References Cited UNITED STATES PATENTS 3,541,98911/1970 Leonard ..114/235 B 3,375,800 4/1968 Cole et a1. ..1 14/235 BInventor:

Assignee:

[ ABSTRACT Apparatus for controlling the depth of water-towed cablessuch as marine seismic cables, such apparatus being remotelycontrollable to run at a predetermined depth under regulation ofhydrostatic pressure responsive mechanism. The apparatus consists ofelectrical transmission and reception circuitry operating in conjunctionwith the seismic cable, and being capable of controlling depthregulating mechanism to operate at one of a plurality of selecteddepths. The depth regulating mechanism includes first and secondcoacting pressure regulator devices, the first regulator device being aregulatory mechanism for varying the diving planes in accordance withthe differential between the ambient hydrostatic pressure and a pre-setvolume of gas under selected pressure, the second device functioning asa servo-follower mechanism to select and control the amount of gaspressure within said pre-set volume at the specified depth.

2 Claims, 10 Drawing Figures 3 680,5 20 I 2 APPARATUS FOR CONTROLLINGDEPTH OF A It is still further an object of the invention to provideWATER-TOWED CABLE BACKGROUND OF THE INVENTION depth keeping apparatusfor use with marine seismic cable apparatus.

2. Description of the Prior Art The prior art includes various types ofparavane instrument as utilized with marine seismic cable and/orhydrophone streamer equipment for the purpose of keeping the trailingmember at a specified depth within a water body. Earlier attempts atdepth-keeping were carried out with some degree of effectiveness bysimply weighting the cable or streamer or by a combination of streamerweighting plus inclusion of low gravity fluid such as light oil having aspecific gravity less than that of sea water. Still other forms ofparavane have been employed and these generally take the form of theclassic end-connected paravane which simply produces a pre-determineddirectional drag on the cable or streamer, but which had little or noregulatory capability.

A prior art teaching which particularly exemplifies the present form ofapparatus is disclosed in U.S. Pat. No. 3,375,800 in the name of Cole eta1. as assigned to the present assignee. This patent teaches the basicfonn of depth controller device wherein the cable or streamer isrotatably directed axially therethrough, and there is included teachingto various control mechanisms which provide the essential scheme asregards the various forms of depth-keeping by means ofpressure-responsive, depth-regulating mechanisms.

SUMMARY OF THE INVENTION The present invention contemplates a marinecable depth controller which is remotely controllable to effect both acoarse depth setting as well as continuous regulatory control about apre-set depth. In a more limited aspect, the invention consists ofpressure regulator mechanism for controlling horizontal control planesof a paravane body or depth controller, the pressure regulator mechanismhaving the capability of both servo-follower and regulatory functions.The regulatory mechanism includes remote control circuitry and apparatusfor varying the gas pressure within a pressure chamber to that valueequivalent to hydrostatic pressure for a pre-determined depth. Anadditional pressure regulation device then takes effect to providecontinuous regulatory adjustment as to the differential between theselected gas pressure and the ambient hydrostatic pressure to maintainthe seismic cable depth controller at the pre-selected depth.

Therefore it is an object of the present invention to provide adepth-keeping apparatus which is remotely controllable from a towingvessel to maintain the towed cable accurately at a selected depth.

It is also an object of the invention to provide several variations ofstructure which are capable of carrying out the basic functions requiredto efiect coarse depthsetting and continuous depth regulation of a cabledepth controller.

- disclosed depth-keeping apparatus which is relatively trouble free andreliable due to the simplicity and essential character of design.

Finally, it is an object of the present invention to provide a seismiccable depth-keeping apparatus which is maintained in dry, secureconditions but in sensing relationship to the ambient hydrostaticpressure at any of a plurality of selected depths.

Other objects and advantages of the invention will be evident from thefollowing detailed description when read in conjunction with theaccompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of thedepth-keeping system including the pressure sensing and regulationapparatus in pictorial block form;

FIG. 2 is a side elevation of a marine cable depth controller showing incutaway a block portion of the control mechanism;

FIG. 3 is a vertical sectional side view of one form of pressureregulator mechanism as constructed in accordance with the presentinvention;

FIG. 4 is a vertical section taken along lines 44 of FIG. 3;

FIG. 5 is a horizontal section taken along lines 55 of FIG. 3;

FIG. 6 is a schematic diagram of a first part of the control circuitutilized in the invention;

FIG. 7 is a schematic diagram of a second part of the control circuitutilized with the invention;

FIG. 8 is a vertical, sectional side view of an alternative form ofdevice which may be built utilizing teachings of the present invention;

FIG. 9 is a block diagram of control circuitry for use with such as thealternative form of mechanism in FIG. 8; and

FIG. 10 illustrates a pressure regulator mechanism and control circuitryin still another alternative form of the invention.

DETAILED DESCRIPTION OF THE DRAWING Referring now to FIG. 1, adepth-keeping system 10 may consist of a transmitting encoder l2transmitting signal energy through one or more input leads 14 fortraverse along such as a marine seismic cable 16. Signal transfer iseffected by a transducer 18 for input to control circuitry 20functioning with a pressure regulator mechanism 22 to controlpositioning of control planes 24 to steer the depth controller in thehorizontal plane.

As shown in FIG. 2, a depth controller 26 receives the seismic cable 16axially therethrough, and is rotatably affixed thereto by means such asthat disclosed in the aforementioned U.S. Pat. No. 3,375,800. The depthcontroller 26 includes the pressure regulator mechanism 22 as well ascircuitry 20 as secured within the vessel housing 28 by suitableaffixture. The details of the vessel housing structure and internaldesign are in the aforementioned U.S. Pat. No. 3,375,800. In thisparticular invention, a further benefit is derived by utilizing anenclosed resilient enclosure or rubber bag 30 both as a protectivemembrane surrounding the pressure regulator mechanism 22 and circuitry20 as well as for a differential pressure transmitting mechanismfunctioning in coaction with pressure regulator mechanism 22, as will befurther described below.

Referring again to FIG. 1, the encoder 12 is essentially a low frequencytransmitter providing characteristic frequency output indicative ofdepth command for transmission along seismic cable 16. In one form ofthe invention, five selected frequencies are employed to enable fivedifferent depth commands. Thus, the five command frequencies may be 313Hz-surface, 349 Hzl ft., 389 112-20 ft., 434 112-30 ft., and 483 Hz-40ft; however, it should be understood that the choice and spacing offrequencies is highly arbitrary. The transducer 18 senses thetransmitted signal at whatever the selected frequency for input tocontrol circuitry 20. Signal coupling through transducer 18 is effectedby means of a ringlike core material 32 surrounding the cable 16 toinduce the characteristic signal through a winding 34 for input to atone amplifier 35. The output of tone amplifier 35 is then appliedthrough a discriminator decoder 36, a well-known form of, circuitry tobe further described, which is responsive to the tone of signal input toprovide an output on one of leads 38. The output on one of leads 38 isthen applied to a reference resistor selector 40 which enables aselected resistor in a resistance bridge network, as will be furtherdescribed below, to provide a predetermined reference voltage output onlead 42 which is directly indicative of a selected depth setting.

The surrounding hydrostatic pressure is effective to actuate a depthsensor 44 to provide an output on lead 46 which is indicative of theactual or instantaneous depth of the system. The depth sensor 44 is awellknown form of resistive device which is pressure responsive. Thereference output 42 and the actual depth output 46 are then applied to acomparator circuit 48 which provides differential output to a poweramplifier 50. The power amplifier 50 provides drive energy to a D-Cmotor 52 which provides rotational output via linkage 54 to pressureregulator mechanism 22. The power amplifier 50 will provide output vialeads 56 and 58, depending upon the polarity of input from comparator48, to drive the motor 52 in one or the other direction, as required bythe particular servofollower function.

The motor 52, a geared-down D-C motor of wellknown type, to be furtherdescribed, provides rotational output via a linkage 54 which is utilizedboth to transmit a force along a linkage 60 to control valve 62, and toprovide a force along a linkage 64' to provide endwise movement of alinkage 66 connected in pivotal affixture to control plane 24. Thelinkage 66 is connected in secure affixture to a diaphragm element 68which, in turn, is supported by a circular, resilient diaphragm member70 within an opening in enclosure 72. Enclosure 72 defines a pressurechamber 74, and it is in communication, for controlled variation througha conduit 76 and valve 62, to a gas supply reservoir 82 as containedwithin a resilient bag 80. Thus, bag 80 is allowed to remain in contactwith the ambient hydrostatic pressure, while defining the gas reservoir82. The interior of depth controller 26 is not maintained watertight,and ambient water pressure on gas bag 80 will tend to force gas fromreservoir 74 through conduit 76 to chamber 74 when valve 62 is open.

FIGS. 3,4, and 5 illustrate one form of pressure regulator mechanism aspresently constructed and utilized in the field. The main body, asexemplified by the main frame 84, is contained in sealed enclosurewithin the rubber bag 30 with a portion of bag 30 serving as thediaphragm element 70. The main frame 84 is hollowed out with a roundinner surface 86 which, in coaction with diaphragm assembly 68 anddiaphragm element 70, forms the chamber 74 therewithin. An end 88 ofmain frame 84 includes an axial bore 90 in communication between gasreservoir 82 and chamber 74, and a poppet valve 92 is inserted in sealedrelationship therein. Thus, poppet valve 92 allows controlledcommunication between gas reservoir 82 and chamber 74 via the passageindicated generally by dash-lines 94. The poppet valve 92 is maintainedclosed by a valve element 96 (FIG. 5) suitably retained to maintainlocking engagement with a valve stem 98. A resilient compound tab havingarms 100 and 101 bears between stem 98 and a suitable form of roller 102extending from a valve actuator arm 104. A notched plate 105 extendsfrom ann 104 for locking contact with a tab 107 integrally connectedwith element 96. The roller 102 may be formed from relatively resilientmaterial such as nylon or teflon and threadedly secured on a screw 106which, in turn, is secured upwardly through valve actuator arm 104. Thepoppet valve 92 is a commercially available type of well-known design asmay be obtained, for example, from the Clippart Corporation ofCincinnati, Ohio.

' At an opposite end 108 of main frame 84, an end block 110 is securelyand sealing received within an end bore 112 of main frame 84. The endblock 1 10 provides secure seating for the DC motor assembly 52 whichprovides rotational input via a shaft 114 through a suitable bearingelement 116 into secure affixture with an actuating cam 118. Theactuating cam 118 includes an eccentric actuating post 120 and it issealingly set against bearing assembly 116 so that a pressure-tight sealis formed between the motor compartment 122 formed within motor housing125 and the interior chamber 74. The motor assembly 52 includes a wellknown type of gear motor which produces low and even fractional RPMoutput in response to DC energization. One form of motor which issuitable is the Globe type No. 43A108-4.

A diaphragm actuating assembly 126 is disposed within chamber 74extending from actuating contact with actuator post 120 to a diaphragmpost 128 which extends in rigid affixture down through diaphragmassembly 68,. The diaphragm actuator assembly 126 includes a pair ofparallel-disposed side plates 130 and 132 which are pivotally affixed bymeans of a pivot pin 134 to opposite sides of diaphragm post 128. Theseside posts 130 and 132 extend toward motor shaft 1 14 to support upperand lower parallel-disposed actuator bars 136 and 138 which are situatedfor interfering relationship to rotation of eccentric actuating post120. Such interference then provides pivotal movement of side posts 130and 132 as they are pivotally affixed by means of a securing pin 140through opposite sides of a securing bracket 142.

An extension of valve actuator arm 104 extends toward the actuating cam118. Thus, a right angle bracket 144 is secured to the top of valveactuator arm 104 with further affixture as by screws to a block 146. Theother side of block 146 is then secured to a right angle bracket 148which includes an extension formed as a vertical actuating arm 150. Theactuating arm 150 is disposed adjacent the eccentric post 120 to belaterally actuated thereby. The block 146, and therefore the remainingbracketed portions of latching arm 104, are pivotally afiixed about avertical pivot pin 152 which is secured through securing bracket 142.

Referring more particularly to diaphragm assembly 68, the diaphragm post128 is rigidly secured through a sealing plate 154, a hole formed withinresilient bag 30, and a central hole 156 through a diaphragm plate 158.Secure and sealed positioning may be assured by the use of such as anepoxy resin cementing the various adjacent elements. A screw 160 is thenthreadedly secured in an upper portion 162 of diaphragm post 128 therebyto affix a right angle bracket 164.

In further defining structure of the linkage 66, a double-hinged plasticelement 166 is rigidly affixed to bracket 164. The double-hinge element166 has a pair of parallel fold margins 168 and 170, and its oppositeend portion 172 is then rigidly secured in a right angle bracket 174which, in turn, is secured as by bolt fasteners or the like to apositioning frame 176 supported from main frame 84. A ring frame 178 issecured around inner surface 86 of main frame 84 to provide a clampingjoinder to press the circumferential areas of diaphragm element 70 (bag30) to main frame 84 in sealing relationship. The positioning frame 176is then securely fastened to an upper surface of ring frame 178.

The positioning frame 176 actually supports the control planes 24(FIG. 1) as they are secured to a support plate 179 which, in turn, isfastened to the center plane 180 of double-hinge element 166 by suitablefastening technique. The support plate 179 extends outboard in thelateral direction by an amount sufficient to provide secure fastening tothe respective control planes 24.

A securing eye 182 is also secured across center portion 180 ofdouble-hinge element 166 to provide a securing position for a spring184. The spring 184 is a tension-type spring which is further stressedby doubling over in its mounted connection. That is, the remaining endof spring 184 is connected to a suitable securing bracket 186, optimallyfastened within the inner housing of the depth controller 26, so thatspring 184 is maintained in a semi-circular attitude or bend. Thus,spring 184 provides a bias force which will tend to maintain supportplate 178 in its horizontal planar position while also eliminatinghysteresis and deadband within the control zone of movement.

FIGS. 6 and 7 illustrate the various parts of control circuitry ingreater detail. Thus, remotely enabled command signals are transmittedvia seismic cable 16 for pick-up through transistor 18, i.e. toroidalcore 32 and induction winding or coil 34, whereupon the command signalis applied to the input tone amplifier 35. The actual control circuitry20 is shown within dashlin'es 200 and is situated on-board the depthcontroller 26 as securely retained within space of reservoir 82 inresilient bag 80 (FIG. 3).

Command input from coil 34 is applied to tone amplifier 35, which may besuch as a two-stage transistor amplifier operating class A in well-knownmanner. It

may also be desirable to utilize field effect transistors in amplifier35 to enable high input impedance and high voltage gain at low supplycurrent. The output from amplifier 35 is then applied via lead 202 tofurther class C amplifier circuitry consisting of NPN-type transistors204 and 206 connected in series. Transistors 204 and 206 are connectedcommon-emitter to intermediate voltage supply lead 208 from themid-connection of series-connected supply batteries 210 and 212 (FIG.7). The batteries 210 and 212 may be such as Eveready type 6-BHIT, 7.5volt cells.

The collector of transistor 204 is connected to a positive voltagesupply lead 214 which is connected through a mercury switch 216 (FIG. 7)to battery supply 210 and, similarly, an additional negative voltagesupply lead 218 is connected through a mercury switch 220 to thenegative terminal of power supply battery 212. The mercury switches 216and 218 serve to disable potential application when the depth controlleris turned past greater than a present lateral angle of role, e. g. wheninverted for storage or shipment.

The transistor 206 also has its collector connected through a relay coil220 of a resonant reed relay 222 to the positive voltage supply lead214. Thus, on conduction of transistor 206, relay coil 220 is energizedto selectively close one of relay contacts 224, 226, 228, 230 or 232.The resonant reed relay 222 may be such as the commercially availabletype known as Bramco model No. RD58. The resonant reed relay ischaracterized by the fact that it will provide but a single relaycontact closure in really contact closure in accordance with thefrequency of energizing signal. While the schematic diagram illustratesa five output resonant reed relay 22, it is entirely a matter of choiceas to the number of channels of command utilized and, therefore, thetype of resonant reed relay employed.

Each of relay contacts 224 through 232 is selectively energized to applyreference voltage from supply lead 208 as adjusted through a resistor234 to the selected one of resistor networks 236, 238, 240, 242 or 244.Each of resistor networks 238 through 244 is constructed in the manneras shown for resistor network 236. That is, each consists of a seriesinterconnection of resistors 246 and a semi-conductive controlledrectifier or SCR 248 with common output provided via a lead 250 to apressure sensitive potentiometer 252 mounted for response toinstantaneous hydrostatic pressure of the surrounds. Each of theresistors 246 within respective resistor networks 236 through 244 isselected to be a distinct and different value so that each is capable ofproducing a null voltage at a different, successively greater depth, aswill be further described below. A particular resistor 246, andtherefore a particular desired depth, is selected by triggering of theSCR 248 in series therewith.

The pressure-responsive potentiometer 252 is connected as a voltagedivider in series with a fixed resistor 254 and a lead 256 through thenormally closed position of relay contacts 258 to reference voltagesupply lead 208. A null or zero output is obtained at the wiper terminalof potentiometer 252 when the depth controller is at proper depth andelectrical balance is achieved.

Sense output from the voltage divider combination is taken via wiperelement of pressure potentiometer 252 on a lead 260 for input to each ofa pair of operational amplifiers, a climb amplifier 262 and a diveamplifier 264. The operational amplifiers 262 and 264 may be acommercially available type such as the National Semiconductor model No.LM201. A pair of diodes 266 and 268 provide zero clamping for respectivepositive and negative feed back inputs. Remaining inputs to each ofoperational amplifiers 262 and 264 are provided by respective resistornetworks 270 and 272 which provide voltage clamping through connectionto lead 274, relay contacts 276 and eventual return to supply lead 208.A diode 278 from each of resistor networks 236 through 244 providesfurther return to stabilize the reference voltage as applied across therespective fixed resistances of resistance networks 236 through 244 andthe pressure potentiometer 252.

Thus, a known output on lead 260 from pressure potentiometer 252 willresult in zero output from each of operational amplifiers 262 and 264.When the pressure potentiometer 252 is below the desired depth, theanalog signal output on lead 260 will be negative and this will causethe operational amplifier 262 to go positive. As operational amplifier262 starts to go positive, the respective feedback circuitry orresistance network 27 will cause the amplifier output to switch withsnapaction from zero to maximum positive voltage no matter how slowlythe input voltage may change.

In the alternative, when the pressure potentiometer 252 indicates abovethe desired depth, the analog output signal on lead 260 is positive.When the signal on lead 260 goes positive, the dive operationalamplifier 264 output switches to maximum negative voltage. In this case,a positive feedback is used for the same reason as before, i.e. as theinput begins to go positive, a slight amount of positive or regenerativefeedback will cause the amplifier output to switch with snap-action fromzero to maximum negative voltage. The action of the operationalamplifier 264 is opposite to that of operational amplifier 262 and, inevent of energization of either, outputs are provided via respectiveoutput leads 280 and 282 to the motor control circuitry.

The output from operational amplifier 262 is applied via lead 280 to thebase of an NPN-type transistor 284 which combines with a PNP transistor286 to form a flip-flop circuit. The collector of transistor 284 isconnected through a relay coil 288 to voltage supply lead 214 such thatrelay coil 288 energizes upon conduction of flip-flop transistor stage284. A despiking diode 290 is connected across relay coil 288.Energization of relay coil 288 will close relay contacts 292 and 294 (asshown) to provide pretermined energization of a D-C motor 296 withinmotor assembly 52. Relay contacts 292 and 294 receive energizing voltagefrom the positive supply voltage lead 214, and deenergization of relaycoil 288 and, therefore, reversal of contact positions of relay contact292 and 294 will result in opposite energization of motor 296.

Positive going voltage on climb input lead 280 is also present through aresistor network 298 and a lead 300 to the gate electrode on an SCR 302thereby to trigger the SCR into conduction enabling a return circuit formotor energization. The cathode of SCR 302 is conducted through thenormally-closed positions of each of a climb microswitch 304 and a divemicroswitch 306 for return via negative supply lead 218 to the negativeinput of battery 212. Microswitches 304 and 306 are integrally containedwithin motor assembly 52, and each is actuated when the motor 296 isrotated to its opposite rotational extremes indicating climb limit anddive" limit directions, respectively. In their opposite actuations,climb microswitch 304 provides connection from negative supply lead 218to a resistor 308 and diode 310 for conduction via lead 312 to the baseof NPN transistor 284 thereby to cut off transistor conduction andrevert the flip-flop action. The microswitch 306 provides the similaraction in the dive condition in that it is actuated to conduct thenegative voltage from lead 218 to a lead 314 and through a resistor 216to the base of PNP transistor 286, as connected common-collector betweenintermediate supply lead 208 and the positive supply lead 214.

An SCR 320 is connected in parallel with SCR 302, to be energizedthrough a microswitch 322 when triggered via gate electrode connectionto lead 324 which connects back through a capacitor 326 and resistor 328to the collector of flip-flop transistor 284. The stop microswitch 322is shown in the normal position wherein the depth controller is in itscontrolling or fine regulation mode. Operation of the stop microswitch322 is effected at the central rotational position of motor 296 to turnoff the SCR 320 which, in turn, controls de-energization of motor 296.

A PNP transistor 330 provides the function of power control. Transistor330 is connected common collector with the collector energized through aload resistor 332 to negative supply lead 218, while the emitter iscoupled to lead 202 which is connected to positive supply lead 214. Thebase of transistor 330 is clamped at a pre-set voltage from positivesupply lead 214, and it is further connected through a diode 334 andcurrent limiting resistor 336 to the normally-open contact of stopmicroswitch 322. Thus, power control transistor 330 is enabled byclosure of stop microswitch 322 whenever the depth controller is not inthe neutral or controlling mode position.

A lead 338 from the collector of transistor 330 is supplied back to arelay control transistor, an NPN transistor 340. The transistor 340provides control of energization of a relay 342 which enablesconservation of battery power when the depth changing portion of thecircuitry is not in use. Thus, when the depth changing circuitry is notused, signal output on lead 338 transistor 330 causes transistor 340 toconduct to energize relay coil 342 such that relay contacts 258 and 276actuate to switch off the pressure potentiometer/voltage dividercircuitry and operational amplifiers 262 and 264. In addition to thecontrol signal from the collector of the power control transistor 330,the relay control transistor 340 may be energized by command signaloutput from any one of the five resistor networks 236 and 244.

Upon a dive command, the operational amplifier 264 will provide anegative output on lead 282 for input to a PNP-type transistor 344 tocause conduction in transistor 344 such that its collector potentialgoes from the negative supply voltage to zero. A positive pulse isconducted from the collector of transistor 344 through lead 300 to thegate electrode of SCR 302 to cause conduction therethrough. Since theflip-flop circuit of transistors 284 and 286 is in the off state, relaycoil 288 is not energized and the motor runs in its reverse direction tomove rotationally toward the dive lock position. When the position isreached, the dive lock position. When the position is reached, the dive"microswitch 306 operates to turn off SCR 302 and motor 296. The divemicroswitch 306, when actuated, applies a negative bias via lead 314 tothe base of transistor 286 which turns off the flip-flop transistorcombination and energizes relay coil 288. Thereafter, when the desireddepth is attained, the dive output from operational amplifier 264switches from the negative voltage to zero thereby to transmit apositive pulse through a resistor 350 and capacitor 352 via lead 324 tothe gate electrode of SCR 320. Motor 296 therefore runs forward untilthe stop microswitch 322 actuates, this indicating that the fins areback in the controlling mode, and the actuation turns off SCR 320 andmotor 296. As previously stated, this actuation also connects negativebias to the base of transistor 284 to de-energize the relay 288.

OPERATION OF THE PREFERRED EMBODIMENT The depth keeping system of thepresent invention utilizes both a servo control function for coarsedepthkeeping and a regulatory function for fine control at the selecteddepths. Thus, remote selection at encoder 12, i.e. one of the specifiedC-W signals, is transmitted along the seismic cable 16 for pick upthrough transducer 18 with subsequent amplification in tone amplifier 35and application to discriminator decoder 36. This selected frequencysignal exercises control over a servo-follower function which will bringthe depth controller 26 to a selected coarse depth whereupon theservo-follower circuitry and mechanism is disabled with the controlplanes 24 in generally horizontal attitude. Thereafter, at thatprescribed depth, the regulatory mechanism consisting of diaphragmassembly 68 and pressure chamber 74 will tend to keep the depthcontroller 26 at the selected depth.

With more particular reference to FIGS. 3 through 7, and otherreferences as noted, the selected frequency command signal is appliedthrough tone amplifier 35 and class C transistor amplifier stages 204and 206 to the resonant reed relay 222. In accordance with frequency,one of contacts 224 through 232 is closed to connect a selectedresistance network 236 through 244 in series with the depth sensor orpressure potentiometer 252. Only when the depth controller 26 comes tothe depth of the selected resistance network 236 through 244 will therebe a null output on lead 260 from pressure potentiometer 252. In anyother event, depending on whether the next selected depth is above orbelow the present cruising depth, one or the other of operationalamplifiers 262 or 264 will be energized. For example, when the commandsignal requires the depth controller 26 to ascend in the water, theoperational amplifier 262 is energized by an output via lead 280 toenergize flip-flop transistors 284-286 thereby energizing relay 388. Atthe same time, the operational amplifier output on lead 280 is appliedvia lead 300 to trigger SCR 302 which enables motor voltage to beapplied through relay contacts 292 and 294 to the drive motor 296 withinmotor assembly 52.

Referring now to FIG. 3, the motor 296 is energized to rotate shaft 114and, therefore, actuating post such that it comes into contact with thelower actuating bar 38 to pivot side posts and 132 about the fulcralsecuring pin thereby to bear upward against pivot pin 134 to move thediaphragm assembly 168 upward. This action results in a lessened totalpressure within pressure chamber 74, even less than the surroundinghydrostatic pressure at the new depth; however, cam action of actuatingpin 120 also provides lateral movement of right angle bracket 148 toswing the actuator arm 104 and roller 102 sideways thereby to releasetab 107 of element 96 to unlock stem 98 of the poppet valve 92. Thepoppet valve 92 is then opened by compressed tab 101 acting on valvestem 98 to allow communication of gas at unequal pressure as betweenreservoir 82 and the pressure chamber 74 thereby to equalize the totalinternal pressure with the surrounding hydrostatic pressure.

To restate, with the controller on depth and the valve stem 98 extendedin closed position, and latched by element 96, the spring arms 100 and101 will be compressed between the end of valve stem 98 and roller 102.This exerts a force against valve stem 98 tending toward valve openposition but it is prevented from such actuation by latching engagementof element 96. When motor 52 responds to a command signal, initiallateral movement of link 104 moves tab 107 of element 96 to unlock valvestem 96. The roller 102 remains on the dwell portion of compressedspring tab 100 which forces valve stem 98 inward to open, and thisinsures opening before diaphragm 70 can move to all pressureequalization.

Only slight further movement of link 104 is required to move element 96via the rigid plate 105 to the valveopen latch position. Continuedmovement of link 104 removes roller 102 from contact with spring 100thereby removing external force from the stem of valve 92 so that theinternal release spring can force the valve 92 closed when element 96 isnext moved in the locking direction by return of rigid tab 107. Thus,the diaphragm 70 is forced to move under power of motor 52 only duringthat position of the stroke of link 104 which is removing spring forcefrom the stem of valve 92, i.e. after the valve is latched open.

When an assigned depth is reached and the motor 52 is energized torotate to the mid-position, the initial movement of link 104 forceselement 96 to its unlatched position and before roller 102 hascompressed spring tabs 100 and 101. Slight further movement of link 104moves element 96 to the valve-closed latching position; and, continuedmovement brings roller 102 into contact to compress spring tabs 100 and101 thereby resetting standby conditions.

After the depth controller 26 comes to its newly selected depth,potentiometer 252 provides a null output and each of climb and diveoperational amplifiers 262 and 264 provide their zero outputs such thatmotor 296 is allowed to reverse to drive the diving planes to theirneutral position. That is, when the motor shaft 114 rotates to enter theclimb" or dive lock position or rotational extreme, the respectiveclimb" or dive microswitch 304 or 306 operates to turn off SCR 302 andthe motor 296. This sequence also de-energizes the flip-flop transistors284 and 286 so that relay 288 is de-energized. De-energization of relay288 enables reverse energization of motor 296 so that the motor runs inthe opposite rotation until the stop microswitch 322 is actuated toindicate that the control planes 24 are back in a controlling orregulatory mode. Operation of the stop microswitch 322 also turns offSCR 320 and the motor 296 to place the circuitry in the stand-by orquiescent operation.

When the motor has returned to its central rotation or stop position,the diaphragm assembly 68 is allowed to remain as suspended betweenoutside hydrostatic pressure and the now-equalized internal pressure ofpressure chamber 74. The poppet valve 92 is once again closed so thatthe hydrostatic pressure for the selected depth as retained withinpressure chamber 74 will remain constant. Thereafter, the depthcontroller 26 is manuevered in its fine control or regulatory modesimply by driving the control planes 24, as connected to support plate179, through vertical movement of diaphragm assembly 68 in response todifferential pressure variations as between the internal pressure ofpressure chamber 74 and the external hydrostatic pressure. The biasspring 184 acts cooperatively with external water pressure to requirethat the gas pressure within chamber 74 be greater than the externalwater pressure through the control zone of diaphragm movement. Thisinsures that diaphragm 70 convolutes outward and can not flop within thesaturation limits of the controller.

Ensuing selections to different depths, as made from the remote positiontake place in the same manner. Thus, sequence also de-energizes theflip-flop transistors 284 and 286 so that relay 288 is de-energized.De-energization of relay 288 enables reverse energization of motor 296so that the motor runs in the opposite rotation until the stopmicroswitch 322 is actuated to indicate that the control planes 24 areback in a controlling or regulatory mode. Operation of the stopmicroswitch 322 also turns off SCR 320 and the motor 296 to place thecircuitry in the stand-by or quiescent operation.

When the motor has returned to its central rotation or stop position,the diaphragm assembly 68 is allowed to remain as suspended betweenoutside hydrostatic pressure and the now-equalized internal pressure ofpressure chamber 74. The poppet valve 92 is once again closed so thatthe hydrostatic pressure for the selected depth as retained withinpressure chamber 74 will remain constant. Thereafter, the depthcontroller 26 is manuevered in its fine control or regulatory modesimply by driving the control planes 24, as connected to support plate179, through vertical movement of diaphragm assembly 68 in response todifferential pressure variations as between the internal pressure ofpressure chamber 74 and the external hydrostatic pressure. The biasspring 184 acts cooperatively with external water pressure to requirethat the gas pressure within chamber 74 be greater than the externalwater pressure through the control zone of diaphragm movement. Thisinsures that diaphragm 70 convolutes outward and can not flop within thesaturation limits of the controller.

Ensuing selections to different depths, as made from the remote positiontake place in the same manner. Thus, in accordance with whether thedepth controller 26 is to be raised or lowered to a new level, motorassembly 52 is driven in one or the other rotations to drive diaphragmassembly 68 such that the diving planes are turned to ascent or descent.Simultaneously, the poppet valve 92 is opened to allow pressurecommunication between the reserve pressure reservoir 82 and the pressurechamber 74 so that it will seek a new internal pressure equal to thehydrostatic pressure at the selected depth. After the depth controlleris brought to the newly selected depth, poppet valve 92 is again closedand diaphragm assembly 68 remains vertically moveable in its regulatorymode to effect correcting planar tilts of the control plan support plate179 in response to pressure variations about the selected hydrostaticpressure.

ALTERNATIVE INVENTION OF FIGS. 8 and 9 FIGS. 8 and 9 disclose analternative and somewhat simplified form of the basic invention. Apressure re gulator mechanism 350 is shown as being comprised of a mainhousing 352 having an open end 354 for communication with surroundinghydrostatic pressure. The main housing 352 includes a generally circularaperture 356 in communication with an internal pressure chamber 358,aperture 356 being covered by a vertically moveable diaphragm assembly360 which is pivotally connected to a turn linkage 362 as secured to atransverse shaft 364 which transmits angular rotation to depth controlplanes 366.

The diaphragm assembly 360 consists of a shaft 368 secured through aclamping portion 370 which is sealingly clamped through a resilientdiaphragm 372 that, in turn, is sealingly connected about the aperture356 on the upper side of main housing 352 by means of a clamping ring374. The lower portion of shaft 368 extends through a descent initiatingcoil 376 suitably secured within said main housing 358 in operativerelationship to shaft 368. A pair of energizing leads 378 are then leadout from pressure chamber 358 for suitable energizing connection atrelated control circuitry within the depth controller. Energization ofthe descent initiating coil 376 will tend to draw shaft 368 and a lowercore portion 380 upward until retained by stop 382 to impartcounterclockwise rotation to linkage 362 in rotation of shaft 364 toimpart descending angle to control planes 366.

Pressure within pressure chamber 358 is varied in accordance with thesurrounding hydrostatic pressure through the action of a piston 384 asdisplaced by a piston rod 386 which is controlled by an electricallycontrolled clamp, i.e. unclamping coil 382 as energized by leads 390 andclamp mechanism 392 and 394 operating in concert. The piston 384 may besuch as an especially designed differential pressure barrier whichincludes a rod extension 396 and former 398 functioning with a firstresilient sealing membrane 400 which is sealingly connected about theinterior of main housing 352 at internal periphery 402, as by suitablefastening means. Similarly, a second resilient sealing membrane 404,circumferentially sealed as at 406, extends across the interior of mainhousing 352 adjacent piston 384 to form an interface adjacent thepressure chamber 358. Energization of unclamping coil 388 frees piston386 for longitudinal movement therethrough so that piston 384 seeks abalance as between the external hydrostatic pressure and that pressurewhich is present in pressure chamber 358.

Referring now to FIG. 9, the control circuit is similar to that which isspecifically described in FIGS. 6 and 7. Thus, control input is appliedat inputs 410 through a suitable amplifier 412 to tone detector 414.Outputs from tone detector 414 provide a signal on lead 416 to a seriesreference resistor network 418, as well as a signal on lead 420 a modeswitch 422. The reference resistor network 418 serves to select apre-determined resistance, as selected in accordance with command input,by actuating a by-passing of one or more of the series resistors424,426,428.

The resistor network 418 is connected in circuit as part of a bridgenetwork, reference resistors 418 being connected in balance with apressure-responsive potentiometer 430 which is maintained in contactwith external hydrostatic pressure. A pair of calibrating resistances432 and 434 complete the bridge connection with a differential amplifier436 being connected between opposite bridge junction points 438 and 440.Voltage unbalance as between junction points 438 and 440 is then sensedand amplified in differential amplifier 436 whereupon one or the otherof an ascent relay 442 or a descent relay 444 is energized, according tothe sense of the output from amplifier 436. The ascent relay 442controls relay contacts 446 which applies positive D-C potential to thebridge circuit, and it also controls relay contacts 448 which energizeunclamping coil 376. The descent coil 444 controls closure of relaycontacts 450 which applies DC potential to the bridge circuit, relaycontacts 452 which control energization of the descent initiation coil376, and relay contacts 454 which energize the unclamping coil 388. Modeswitch 422 is closed by signals from tone detector 414 to enable DCpotential application to the bridge circuit whenever any command signalis received through tone detector 414.

In operation, the individual resistors 424, 426 and 428, which incombination constitute reference resistor network 418, may be selectedto have resistance values in binary sequence; that is, each value ofresistance is double the value of the next lowest resistance, and ifeach signal frequency which can be transmitted to and received by thetone detector 414 is made to leave one particular value of resistance inthe bridge circuit, then the combination of three resistors and threetones is such that a total of seven pre-deterrnined depths will beavailable to assign to the controller. It is assumed that the controllerhas been running at a particular depth and that, for purposes ofoperational explanation, the controller will be placed at a new depthbelow the present running depth. Thus, one or more tones are transmittedcorresponding to the binary setting which is desired.

Upon receipt by tone detector 414, one or more of resistors 424 through428 are placed in circuit and the mode switch 422 is closed to place D-Cpotential on the bridge circuit. Since the controller is presently at ahigher elevation than the newly selected depth, the resistance ofpressure potentiometer 430 will not be sufiicient to balance the bridgecircuit, and an anti-null signal will appear at the input todifferential amplifier 436. The output from amplifier 436 will thenactuate descent relay 444 to close the relay contacts 450, 452 and 454.Closure of the relay contacts maintains D-C potential on the bridgecircuit while energizing both the descent coil 376 and the unclampingcoil 388, and the circuit will remain in this state until the descent ofthe depth controller brings it to the pre-selected depth at which thepressure potentiometer 430 will again produce a null input todifferential amplifier 436.

Upon production of the null, the descent function relay 444 drops out ofenergization to open its respective contacts and to de-energize thebridge circuit. The mechanism has then fulfilled its servo-follower orcontrol mode and is then placed in the regulatory mode of operation.That is, pressure within pressure chamber 358 is properly balanced asopposed to external hydrostatic pressure such that minute variations indepth controlling position are corrected through movement of diaphragmassembly 360 to cause correctional variations of control planes 366.

When D-C potential is applied across descent coil 444, the magneticforce urges shaft 368 in the upward direction placing the control planes366 in a descending attitude. The application of D-C potential to theunclamped coil 388 causes release of the clamping mechanisms 390 and 394so that the piston 384 and rod 386 become freely moveable to seek theirown positions as balanced between the internal pressure within pressurechamber 358 and the external hydrostatic pressure. Inward movement ofpiston 384 maintains internal gas pressure equal to the external outerpressure. When the controller reaches proper depth and assumes itsregulatory mode, the clamps 390 and 394 lock the piston rod 386 in itsnewly assumed position. Since the internal gas pressure is now equal toexternal outer pressure, the bias spring 367 will move the controlplanes 366 to an ascending position until the external water pressurediminishes by the magnitude of the bias spring force divided by the areaof primary diaphragm 372. The vertical movement represented by thispressure reduction will typically be but a few inches and negligible intotal.

ALTERNATIVE FORM OF FIG. 10

FIG. 10 disclosed still another variation on the basic design whichincludes capability of a control mode and a regulatory mode ofoperation. A pressure regulator mechanism 460 consists of an expansionchamber 462 which is in communication with surrounding hydrostaticpressure and which is connected by means of a sealed conduit 464 andsolenoid-controlled valve 466 to a main frame 468. The main frame 468defines a pressure chamber 470, and is integrally constructed with adiaphragm assembly 472 which forms an interface with the ambienthydrostatic pressure surrounds. The diaphragm 472 connects through apivotal linkage 474 and shaft 476 to drive guide planes 478 as biasedupward by means of bias spring 480 suitably fastened within theassociated depth controller structure.

The diaphragm assembly 472 consists of a diaphragm plate 482 whichreceives resilient membrane or diaphragm 484 in sealed relationshipabout the periphery by suitable fasteners. The interior portions ofdiaphragm 484 are fixed within clamping plates 486 as secured along apiston rod 488 which is pivotally secured to linkage 474. A threadedportion 490 of diaphragm plate 482 is threadedly received in sealedrelationship within a collar portion 492 forming a communication withpressure chamber 470. The diaphragm piston rod 488 is received downthrough an axial bore 494 in collar portion 492 while allowing aremaining air passage space 496 therealong. An electrical coil 498 issuitably secured within collar portion 492 around piston rod 498 whileelectrical leads 500 are lead outward to the related control circuitwithin the depth controller. The piston rod 488 is formed of suitablecore-like material such that it is responsive to electrical current flowthrough coil 498 to move endwise therein.

An end cap 502 is threadedly secured in sealed relationship through anend 504 of main frame 468, its purpose being to house a pressure withinpressure chamber 470, electrical output being via leads 508 to controlcircuitry 510 which would be suitably disposed within the depthcontroller.

Expansion chamber 462 includes an expansible interface 512 which issealingly connected within chamber 462 and in communication withexternal hydrostatic pressure via orifice 514. Thus, interface 512 iscapable of expanding and contracting in volume within internal space 516of expansion chamber 462. In turn, the internal chamber 516 transmitsvariations in pressure through conduit 464 to valve 466. The solenoidvalve 466 can then be actuated by suitable input from control circuitry,as will be further described, to open the valve and allow pressurecommunication and equalization with pressure chamber 470. It is alsocontemplated that additional control inputs may be utilized to provideopening of the control valve 466. For example, a bottom contact lever(not shown) may be utilized to open conduit 464 and allow pressureequalization to cause emergency ascent of the depth controller.

The control circuitry of FIG. is similar to that described with respectto the foregoing embodiments of the invention. The seismic cable 16 issensed for control signal by means of a toroidal core 520 and sensewinding 522 to provide input to a standard form of amplifier 524. Outputfrom amplifier 524 is then applied through a tone detector 526 toprovide an output selection of pre-scribed resistance in a resistornetwork 528 within a bridge circuit indicated generally as 530. Thebridge circuit 530 consists of the selectable resistor network 528,pressure potentiometer 506 within pressure chamber 470, and a pair ofcalibrating potentiometers 532 and 534. Output from the bridge circuitis taken between leads 536 and 538 for input to a differential amplifier540 which provides a sense output to control relay 542. The outputs fromcontrol relay 542, leads 544 and 546, are applied to control respectiveactuations of pressure regulator mechanism 560. Thus, output on lead 544actuates solenoid-control valve 466 to permit pressure equalization asbetween internal chamber 516 and the pressure chamber 470, while outputon lead 546 energizes the relay coil 498 to draw diaphragm shaft 488upward thereby to place the planes 478 in the dive or descent position.The spring bias 480 is adjusted to sufficient force such that it carriesout the ascent function, and is counter-acted merely by periodic andcontrolled output from control relay 542 on lead 544 to thesolenoid-controlled relay 466 to effect proper pressure equalizationbetween pressure chamber 470 and the surrounds.

The foregoing discloses novel designs for effecting accurate andreliable control of one or more cable de th controllers from a remote sii n or comman po t such as aboard a towing ves l. e apparatus 0 theinvention is especially advantageous in that it enables both rapidcoarse adjustment of operating depth through a servo control mechanismand it provides additional fine control about a selected depth by meansof relatively simple and reliable mechanical structure.

Changes may be made in the combination and arrangement of elements asherefore set forth in the specification and shown in the drawing; itbeing understood that changes may be made in the embodiments disclosedwithout departing from the spirit and scope of the invention as definedin the following claims.

What is claimed is:

1. Apparatus for controlling the depth of a seismic cable depthcontroller assembly which includes depth adjusting control planes,comprising:

first chamber means including as an integral part of a wall thereof adiaphragm portion which is resiliently moveable to provide a pressureadjustable interface between internal chamber pressure and ambienthydrostatic pressure at said depth controller;

linkage means connected between said diaphragm portion and said controlplanes to provide proportional control plane angular adjustment inresponse to displacement of said diaphragm portion due to differentialpressure across said interface;

expansible chamber means in contact with said ambient hydrostaticpressure and containing gas under nominal pressure, said expansiblechamber means including valve-controlled conduit means for placing saidexpansible chamber means in communication with said first chamber means;and

control means to drive said linkage means such that the control planesguide said depth controller to a predetermined depth and,simultaneously, to open said valve-controlled conduit means to allowpressure equalization between said expansible chamber means and saidfirst chamber means, said control means additionally comprising:

actuation means doubly hinged for movement in two planes and responsiveto said control actuation means disposed within said first chamber meansin connection to drive said linkage means and to open saidvalve-controlled conduit means; and

actuation control means energized by said control means and beingdisposed to transmit actuation control into said first chamber means tosaid actuation means.

2. Apparatus as set forth in claim 1 which is further characterized toinclude:

a resilient sealed bag enclosure which envelopes said first chambermeans while forming said diaphragm portion of the first chamber means,said enclosure forming the expansible chamber means.

1. Apparatus for controlling the depth of a seismic cable depthcontroller assembly which includes depth adjusting control planes,comprising: first chamber means including as an integral part of a wallthereof a diaphragm portion which is resiliently moveable to provide apressure adjustable interface between internal chamber pressure andambient hydrostatic pressure at said depth controller; linkage meansconnected between said diaphragm portion and said control planes toprovide proportional control plane angular adjustment in response todisplacement of said diaphragm portion due to differential pressureacross said interface; expansible chamber means in contact with saidambient hydrostatic pressure and containing gas under nominal pressure,said expansible chamber means including valve-controlled conduit meansfor placing said expansible chamber means in communication with saidfirst chamber means; and control means to drive said linkage means suchthat the control planes guide said depth controller to a predetermineddepth and, simultaneously, to open said valve-controlled conduit meansto allow pressure equalization between said expansible chamber means andsaid first chamber means, said control means additionally comprising:actuation means doubly hinged for movement in two planes and responsiveto said control actuation means disposed within said first chamber meansin connection to drive said linkage means and to open saidvalve-controlled conduit means; and actuation control means energized bysaid control means and being disposed to transmit actuation control intosaid first chamber means to said actuation means.
 2. Apparatus as setforth in claim 1 which is further characterized to include: a resilientsealed bag enclosure which envelopes said first chamber means whileforming said diaphragm portion of the first chamber means, saidenclosure forming the expansible chamber means.